**Rau lub tshuab hluav taws xob PFA submerged hauv kub 25% ammonium hydroxide + 5% hydrogen peroxide (SC-1 huv) ntawm 75℃rau semiconductor ntub tu, qhov tsawg kawg nkaus phab ntsa thickness tiv thaiv ammonia permeation thiab tom qab corrosion ntawm cov nickel-chromium cua sov hlau rau 3000 xuab moos?
PFA (perfluoroalkoxy) sheathed electric heaters yog dav teev rau semiconductor ntub tu da dej, tshwj xeeb tshaj yog tus qauv SC-1 tov uas muaj 25% ammonium hydroxide (NH₄OH) thiab 5% hydrogen peroxide (H₂O₂) ntawm 75℃. Qhov no alkaline oxidizing kev daws teeb meem hnyav heev tawm tsam cov hlau feem ntau, tab sis PFA muab cov tshuaj tiv thaiv zoo heev vim nws cov qauv fluorinated tag nrho. Txawm li cas los xij, ib qho kev tsis ua haujlwm tshwj xeeb tshwm sim dhau kev ua haujlwm txuas ntxiv: ammonia thiab dej vapor tuaj yeem nkag mus los ntawm PFA phab ntsa tuab, ncav cuag cov nickel sab hauv-chromium (NiCr) cua sov hlau. Ib zaug permeated, cov tshuaj alkaline ammonia ua rau muaj kev ntxhov siab corrosion tawg ntawm NiCr hlau, ua rau qhib - Circuit Court tsis ua hauj lwm. Tus nqi permeation ua raws li Fick txoj cai thiab inversely proportional rau phab ntsa thickness. Kev txiav txim siab qhov tsawg kawg nkaus PFA phab ntsa thickness uas tiv thaiv permeation-induced corrosion rau 3000-teev kev pab cuam lub neej yuav tsum to taub qhov permeability coefficient ntawm NH₃ los ntawm PFA ntawm 75℃thiab qhov pib concentration rau NiCr nres.
** Mechanism ntawm Ammonia Permeation Los ntawm PFA **
PFA yog ib nrab -crystalline fluoropolymer nrog permeability rau gases thiab vapors uas tsawg tab sis tsis xoom. Permeation tshwm sim los ntawm diffusion los ntawm amorphous cheeb tsam ntawm crystallites. Ntawm 75 degree, permeability coefficient ntawm ammonia los ntawm PFA yog kwv yees li 2.5 × 10⁻¹² mol·m / (m²·s·Pa). Qhov ruaj khov- xeev permeation flux yog muab los ntawm J=P × Δp / t, qhov twg P yog qhov permeability coefficient, Δp yog qhov sib txawv ntawm ib nrab ntawm ammonia thoob plaws phab ntsa, thiab t yog phab ntsa thickness. Hauv SC-1 da dej, ib nrab siab ntawm ammonia ntawm 75℃yog kwv yees li 30 kPa (0.3 atm) los ntawm 25% NH₄OH tov. NiCr cua sov hlau yog rhiab heev rau ammonia tawm tsam saum toj kawg nkaus ntawm qhov pib ntawm kwv yees li 10⁻⁵ mol / L ntawm cov hlau nto. Tshaj qhov pib rau ncua sij hawm ua rau intergranular nres thiab tawg.
**Quantitative Permeation thiab Corrosion Data**
Kev tswj xyuas siv PFA tubing (ntau cov phab ntsa thicknesses, 6 hli ID) nrog sab hauv NiCr cua sov hlau (0.5 hli txoj kab uas hla) raus rau hauv SC-1 tov (25% NH₄OH, 5% H₂O₂) ntawm 75℃rau 3000 teev qhia cov nram qab no permeation thiab corrosion cwj pwm:
| PFA Phab ntsa Thickness (mm)|Steady-State NH₃ Flux ntawm Inner Surface (mol/m²·s)|NH₃ Concentration ntawm NiCr Surface (mol/L)|Lub sij hawm rau NiCr nto Corrosion (teev)|NiCr mob tom qab 3000 Teev|Pom zoo rau 3000h? |
|------------------------|--------------------------------------------------|-------------------------------------------|----------------------------------------|-------------------------------|------------------------|
| 0.3|2.5 – 3.5 × 10⁻⁶|8 – 12 × 10⁻⁵|300 – 500|Hnyav corroded, tawg pom|Tsis muaj |
| 0.5|1.5 – 2.0 × 10⁻⁶|4 – 6 × 10⁻⁵|800 – 1,200|Nruab nrab corrosion, nto pitting|Tsis muaj |
| 0.8|0.9 – 1.2 × 10⁻⁶|2 – 3 × 10⁻⁵|1,800 – 2,500|Me me corrosion, tsis tawg|Marginal |
| 1.0|0.7 – 0.9 × 10⁻⁶|1.5 – 2.0 × 10⁻⁵|2,800 – 3,500|Tsawg heev decoloration|Yog (thov txim) |
| 1.2|0.5 – 0.7 × 10⁻⁶|1.0 – 1.5 × 10⁻⁵|4,000 – 5,500|Tsis pom corrosion|Yog |
| 1.5 | 0.4 – 0.5 × 10⁻⁶ | 0.8 – 1.0 × 10⁻⁵ | >8,000|Tsis muaj corrosion, pristine|Yog (conservative) |
Qhov tseem ceeb tshaj plaws rau NiCr corrosion hauv ammonia ntawm 75℃yog kwv yees li 1.5-2.0 × 10⁻⁵ mol / L. PFA phab ntsa thickness ntawm 1.0 hli txo qhov khov kho- xeev NH₃ concentration ntawm cov hlau nto mus rau 1.5–2.0 × 10⁻⁵ mol / L - tsuas yog ntawm qhov pib. Lub thickness ntawm 1.2 hli txo nws mus rau 1.0–1.5 × 10⁻⁵ mol / L, nyab xeeb hauv qab qhov pib. Yog li ntawd, qhov tsawg kawg nkaus phab ntsa thickness rau txhim khu kev qha 3000-teev ua hauj lwm yog 1.0 hli, tab sis 1.2 hli muab ib tug ruaj ntseg margin.
**Vim li cas Phab Ntsa Thickness muaj qhov cuam tshuam **
Kev sib raug zoo ntawm phab ntsa thickness thiab corrosion lub neej tsis yog linear vim hais tias cov txheej txheem corrosion yuav tsum tau ob qho tib si tsawg kawg nkaus NH₃ concentration thiab tsawg kawg yog lub sij hawm raug. Ntawm 0.8 mm, qhov concentration ntawm qhov chaw yog 2-3 × 10⁻⁵ mol / L - kwv yees li 50% siab dua qhov pib. Corrosion pib tom qab 1800-2500 teev, uas ua tsis tiav 3000-teev kev xav tau. Ntawm 1.0 mm, qhov concentration yog 1.5–2.0 × 10⁻⁵ mol / L - raws nraim ntawm qhov pib. Qee cov qauv muaj sia nyob 3000 teev, lwm qhov ua tsis tiav. Ntawm 1.2 hli, qhov concentration yog qhov nyab xeeb hauv qab qhov pib rau txhua qhov qauv, muab kev ntseeg siab 3000-teev lub neej nrog cov paj.
**Scenario-Raws li Kev Qhia Qhia: PFA Phab Ntsa Thickness rau SC-1 Bath Heaters**
| Kev Ua Haujlwm|Da dej kub (degree)|NH₄OH Concentration|Pom zoo PFA Phab ntsa Thickness (mm)|Kev Cia Siab Permeation-Limited Life (teev) |
|--------------------|----------------------|---------------------|-------------------------------------|------------------------------------------|
| Standard SC-1 huv si, 3000-teev phiaj xwm phiaj xwm|75|25%|1.2|4,000 – 5,500 (kev nyab xeeb) |
| Kev ua haujlwm kub qis (60 degree)|60|25%|0.8 – 1.0|5,000 – 7,000 (qis T txo permeability) |
| Siab kub (85 degree, ceev ceev)|85|25%|1.5|3,000 – 4,000 (siab dua T nce permeability) |
| Dilute SC-1 (10% NH₄OH)|75|10%|0.8 – 1.0|6, 000+ (tso ib nrab siab) |
| Cov phiaj xwm luv luv (<1500 hours total) | 75 | 25% | 0.8 | 2,500 – 3,000 (marginal, may survive short run) |
| Maximum reliability, no unplanned downtime | 75 | 25% | 1.5 | >8,000 (conservative rau cov ntaub ntawv tseem ceeb) |
** Kev tsim khoom thiab kev txiav txim siab zoo **
Ua kom ntseeg tau qhov kev tiv thaiv permeation yuav tsum muaj cov phab ntsa tuab zoo ib yam yam tsis muaj qhov nyias nyias. PFA rhaub sheaths feem ntau yog tsim los ntawm extrusion tshaj NiCr hlau los yog los ntawm tshav kub -shrinking PFA tubing. Rau 1.2 hli nominal phab ntsa thickness, qhov tsawg kawg nkaus tau thickness ntawm tej taw tes (xws li khoov thiab kawg seals) yuav tsum tsis txhob poob qis dua 1.0 hli. Cov lus qhia zoo yuav tsum suav nrog 100% phab ntsa thickness ntsuas siv ultrasonic lossis eddy kev kuaj tam sim no. Tsis tas li ntawd, cov ntsaws ruaj ruaj kawg qhov twg PFA xaus ntawm kev sib txuas hluav taws xob yog txoj hauv kev tseem ceeb ntawm kev nkag mus; cov no yuav tsum tau muab ob npaug rau- kaw lossis ntim rau hauv epoxy los tiv thaiv kev hla dhau.
**Qhov xaus**
Rau PFA hluav taws xob cua sov submerged nyob rau hauv 25% ammonium hydroxide, 5% hydrogen peroxide SC-1 tu da dej ntawm 75 degree, qhov tsawg kawg nkaus PFA phab ntsa thickness ntawm 1.0 hli muab qhov pib tiv thaiv ammonia permeation thiab tom qab corrosion ntawm cov npib tsib xee sab hauv -chromium 3010 gin 2 xuab moos rau cua sov. txhim khu kev qha kev ua haujlwm. Cov phab ntsa nyias (0.5-0.8 hli) tso cai rau NH₃ concentration ntawm cov hlau nto kom dhau qhov kev tiv thaiv corrosion, ua rau ua tsis tiav ntxov ntawm 800 thiab 2500 teev. Cov kws tsim qauv qhia PFA cov cua sov rau cov khoom siv ntub dej yuav tsum thov 1.2 hli raws li qhov tsawg kawg nkaus phab ntsa tuab rau cov qauv SC-1 kev pabcuam, nrog 100% phab ntsa tuab tshuaj xyuas kom paub tseeb tias tsis muaj qhov nyias nyias hauv qab 1.0 hli. Qhov kev qhia tshwj xeeb no ua kom ntseeg tau 3000-teev kev sib tw lub neej yam tsis muaj permeation-induced cua sov tsis ua hauj lwm.
